Angolatitan adamastor, a new sauropod dinosaur and the first record from Angola

A forelimb of a new sauropod dinosaur (Angolatitan adamastor n. gen. et sp.) from the Late Turonian of Iembe (Bengo Province) represents the first dinosaur discovery in Angola, and is one of the few occurrences of sauropod dinosaurs in sub-Saharan Africa collected with good chronological controls. The marginal marine sediments yielding the specimen are reported to be late Turonian in age and, thus it represents a non-titanosaurian sauropod in sub-Saharan Africa at a time taken to be dominated by titanosaurian forms. Moreover, Angolatitan adamastor is the only basal Somphospondyli known in the Late Cretaceous which implies in the existence of relict forms in Africa.


INTRODUCTION
Although very rich in Cretaceous vertebrates, Angola has remained unexplored in recent decades.Beginning in 2005, the field work conducted by the PaleoAngola Project has significantly enhanced the palaeontological record of the Cretaceous of Angola (Jacobs et al. 2006, 2009a, b, Polcyn et al. 2009, Mateus et al. 2008, Schulp et al. 2008).The PaleoAngola Project mounted the first systematic paleontological expeditions that have been conducted since the early 1960s, when Miguel Telles Antunes performed an extensive and systematic survey on the Angolan fossil vertebrate fauna the most relevant work published in 1964 (Antunes 1964).In May 2005 we (O.M. and L.J.) prospected the coastal area near OM), of the new taxon reported here.Follow-up vations were performed in May and August 20 our knowledge, it was the only systematic prosp for fossil vertebrates in this area since 1960 by M Antunes (in September) and M. Mascarenhas Ne While the lush vegetation in most inland precludes fossil prospecting, the exposures alo Atlantic coastline in Ambriz municipality allow tematic prospecting.The material collected PaleoAngola Project is largely housed at Museu lógico da Universidade Agostinho Neto (MGUA Luanda, while some of the collected mosasaur, saur, pterosaur, and turtle specimens are temp housed at Museu da Lourinhã (ML), Portuga Southern Methodist University (SMU) in Dal "main" -2011/2/10 -15:47 -page 222 -#2

GEOLOGY AND ASSOCIATED FAUNA
The term 'Tadi beds' was first coined in the 1960 unpublished study of G. Brognon , G. Verrier, and R Thiers "Géologie du Bassin du Cuanza et du Bas-Congo" from the "Missão de Pesquisas de Petróleo Petrofina".It was accepted and used by Antunes (1964) and Antunes and Cappetta (2002).The original study considered the 'Tadi Beds' to represent the base of the 'Senonian' (= Coniacian), but the fish fauna led Antunes (1961Antunes ( , 1964: 56) : 56) to consider the Tadi Beds to be of late Turonian age.In a revision of the Cretaceous selachians of Angola, Antunes and Cappetta (2002: 95) reconfirm the late Turonian age of these beds, and place them in the 'Itombe Formation' (see also Jacobs et al. 2006).The Tadi Beds are about 50 m thick (Antunes 1964: 56).G.The tetrapod fauna from the Iembe locality (Antunes 1964, Jacobs et al. 2006;and new unpublished data) includes an eucryptodiran turtle Angolachelys mbaxi (Mateus et al. 2009), the mosasaurs Angolasaurus bocagei Antunes 1964 (see also Polcyn et al. 2009) and Tylosaurus iembeensis (Antunes 1964, Lingham-Soliar 1992), Plesiosauria indet., and the sauropod material described here.The discovery here reported is the first dinosaur and the first Cretaceous terrestrial animal from Angola.

SYSTEMATICS PALEONTOLOGY
Dinosauria Owen, 1842 Sauropoda Marsh, 1878 Neosauropoda Bonaparte, 1986 GENERIC AND SPECIFIC DIAGNOSIS Titanosauriform sauropod with: posteroventral eminence in scapula in the proximal one-quarter, anterior to the acromial ridge; acute medioproximal margin of humerus; and rectangular lateral corner of proximal humerus; proximal outline of the ulna with anteromedial ridge (process); posterior facet of the distal epiphysis of metacarpal I with two small splint-like projections (Figs. 3 and 5).

MATERIAL
The material includes a partial right forelimb including the scapula, humerus, ulna, radius and metacarpals I, III, and IV (Table I).All material described here is curated at Museu de Geologia da Universidade Agostinho Neto -PaleoAngola Project, Luanda, Angola (MGUAN-PA), and temporarily registered under field number MGUAN-PA-003 (replicas will be housed at Museu da Lourinhã, Portugal, and at Southern Methodist University, USA).

DESCRIPTION
However, this could be a case of taphonomical tion.The proximal end is incomplete, but does no very expanded.The scapular blade is 16.5 cm, w ventral supraglenoid expansion just above it, and on the maximum dorsal expansion.The ventral glenoid expansion is 65 cm in its maximum ante terior width, therefore representing nearly four the minimum width of the blade.For the descr the orientation of the scapula adopted here is w scapular blade in a vertical dorsal position as in (1956).
The blade is rectangular in cross section, with  anteriorly, forming a gentle curve in its anterodorsal corner due to the absence of the dorsal hook.
The medial surface is gently concave in all its extension, except in a small (ca.6 cm) shallow bump placed at the anterior part at the base of the scapular blade, and in the bump in the posteromedial margin of the scapula about 20 cm above the glenoid.
The contact surface between the coracoid and glenoid is perpendicular with the blade in a posterior or anterior perspective, but the contact with the coracoid runs slightly dorsally, forming a 20 • angle with the horizontal (if the scapula is arranged upwards).The ally glenoid is apomorphic of Somphospondyli according to Wilson 2002 (character 153).
The ventroposterior margin of the scapula, adjacent to the glenoid, projects posteriorly and has a small (ca.9 cm) vertical ridge that borders a groove somewhat similar to Cetiosaurus oxoniensis.A posteroventral bump in the scapula in the proximal one-quarter is shared/convergent with Dystrophaeus and Supersaurus, Ultrasaurus mcintoshi, Lourinhasaurus alenquerensis, and Camarasaurus supremus, but, unlike other sauropods, it is anterior to the acromial ridge.The glenoid foramen is not visible.gracile with a straight shaft.The proximal end is Lshaped due to the well-defined deltopectoral crest.The humeral head is well developed and more projected anteriorly than the lateral corner, which gives an asymmetrical outline in anterior view.The lateral corner forms a rectangular corner (rather than a round corner more commonly seen in sauropods) and a straight line to the most proximal part of the humerus.The medioproximal corner of the humerus is very pointy due to a 4 cm margin.The tip of the deltopectoral crest projec anteromedially, invading the anterior side of the A medially projected deltopectoral crest is pre Titanosauriformes more derived than Brachios The bump placed lateromedially to the tip of de toral crest gently projects laterally, making a wid for muscle attachment.Except for this bump, the margin is totally straight.A hemispherical humer projects well posteriorly.The diaphyseal cross "main" -2011/2/10 -15:47 -page 226 -#6

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OCTÁVIO MATEUS et al.  epiphyseal expansions.The maximum proximal width equals about 25% of the full length of the radius.The proximal end is sub-round, while the distal end is flattened and elongated with an anteroposterior expansion.
The medial edge of the distal epiphysis is acute, but the lateral is round.The posterior face of the distal epiphysis bears a groove at the ulnar articulation procuding two shallow posterior condyles.The medial part projects more distally forming a bevelled angle with the main shaft.Three metacarpals (I, III and IV) were present near the distal end of the ulna.With the exception of the bone surfaces exposed to weathering prior to discovery, the bones do not show signs of crushing or deformation.The metacarpal position was identified as I, III, and IV using Janensch (1961), Apesteguía (2005) and Bonnan and Wedel (2004).The metacarpals are elongated, much more than in titanosaurs.All metacarpals are nearly of the same size, but III is the largest and IV is the shortest preserved element.The distal end bears sutble but separated distal condyles which is a plesiomorphic condition because the presence of divided condyles is normally associated with the presence of phalanges, lost in titanosaurs (Wilson 2002, Upchurch et al. 2004).The metacarpals bound together by the extensive diaphyseal articulation to form a tubular arrangement, U-shaped in proximal view.The length ratio between metacarpal III and the radius is 0.48.A ratio higher than 0.45 is used to be considered a character medial corner more rounded than the lateral.The carpal presents a crest along the whole lateral fac with a sinosoidal area at midshaft.The distal transversely broad, with two well-defined condyl less visible than in non-macronarian sauropods) d by distal and posterior grooves, the lateral condyle smaller than the medial.The posterior facet of th epiphysis has two small splint-like projections: o above the intercondylar groove and the other n lateral condyle, which is autapomorphic.
The right metacarpal III is complete, with ception of a portion of the lateral distal condyle subtriangular in proximal view.Ligament attach on the palmar surface occupy almost the entire mal half of the metacarpal -which also represe area of contact with metacarpal IV.The medial fa an acute crest along the diaphysis that is divided proximal third, and rims a large facet facing ant dially.The distal end shows defined condyles, be lateral one the largest.
The metacarpal IV is robust.In the pr view it is triangular, with the anterior margin be widest.The proximal surface is flat, but the do dial corner which is projected medially deflects d forming a 45 • angle with the proximal surface.T tal end is transversely broad and presents two co divided by a medial vertical intercondylar groo there is no distal intercondylar groove.This bo sembles the metacarpal IV of cf.Laplatasaurus "main" -2011/2/10 -15:47 -page 228 -#8
There are no signs of other carpals, metacarpals or phalanges, but the lateral flattening on metacarpal IV suggests the possible presence of metacarpal V, and the distal condyles suggest the presence of phalanges.
In Angolatitan adamastor, the metacarpals do not show three titanosaurian characters considered by Apesteguía (2005): bowed metacarpal I, the flat distal metacarpal trochlea (although this is difficult to quantify), and reduced intermetacarpal contact that is 1/6 of the metacarpal length.
The data matrix was based in Wilson (2002), but the integration of characters in Upchurch et al. (2004) for the forelimb (Angolatitan coding using Wilson 2002, using WinClada ver 1.0 (www.cladistics.com)using a heuristic search with 100 replicates.Angolatitan adamastor n.gen.et sp.was placed as a basal titanosauriform Somphospondyli more derived than Brachiosaurus, but less derived than Euhelopus (see Fig. 6).The metacarpals are slender (close to Camarasaurus proportions and alike titanosaurs as Opisthocoelicaudia, when compared in the plot provided by Bonnan and Wedel 2004).The robustness (ratio minimum diaphyseal perimeter/length) is 0,42, which is lower than the range of 0,5-0,6 in most titanosaurs (Apesteguía 2005: Table 15.2).The size of metacarpals is equivalent (being of variable length in Titanosauridae, see Apesteguía 2005), and the distal end is round, rather than flat as in Titanosauridae.
The Angolatitan adamastor is supported as Somphospondyli by the following unambiguous synapomorphies: humeral square proximolateral corner (character 159 in Wilson 2002), deltopectoral crest medially expanded across the cranial face of the humerus (ch.220 in Upchurch et al. 2004), and distalmost part of the caudal surface of the humerus deeply concave between the lateral and medial prominent vertical ridges (ch.221 in Upchurch et al. 2004).However, the scapular glenoid surface faces cranioventrally (ch.203 in Upchurch et al. 2004) unlike Euhelopus and other derived Somphospondyli.The Angolan sauropod does not bear titanosaurian synapomorphies such as the ulna with prominent olecranon process (Wilson 2002: character 167) or extremely robust ulna and radius (Upchurch et al. 2004: 309).

GEOGRAPHY AND CHRONOLOGY
Although sauropod dinosaurs have been reported from elsewhere in Africa, (e.g.Algeria, Cameroon, Egypt, Kenya, Malawi, Mali, Morocco, Niger, South Africa, Sudan, Tunisia, Zambia, Zimbabwe, and Madagascar), no others are known from the Late Turonian.The only described Late Cretaceous sauropods from Africa are the lithostrotian titanosaurs Aegyptosaurus baharijensis rus krausei and "Titanosaurus" madagascariensis from Madagascar (Campanian; Curry Rogers andForster 2001, Weishampel et al. 2004).Globally, the circa-Turonian sauropods were found only in Argentina, Brazil, and China (Table II), and comprise mostly titanosaurs or diplodocoids.Thus, A. adamastor fills a 15My gap in the African sauropod record, and an even wider gap in the global record of non-titanosaur sauropods.
Non-titanosaur sauropods, which were dominant during the Jurassic, were being replaced by titanosaurs and derived diplodocoids, becoming rarer in the Late Cretaceous when most identifiable African sauropods were titanosaurs.The reasons for the late Cretaceous dominance of titanosaurs over other sauropods are not fully understood, but it seems to be a general pattern in South America, in Madagascar, and probably in Africa chronology and even taxonomy of these saurop not well understood for the Late Cretaceous of Diplodocoids were the most successful non-tita sauropods in the Cretaceous, but the presence o sible brachiosaurids (Rauhut and Werner 1997) questions regarding the paleogeography of saurop The age of the sediments yielding the speci Upper Turonian (∼90Ma) based on the fish and teeth (Antunes and Cappetta 2002) and, thus, is the best-dated Late Cretaceous sauropod specim sub-Saharan Africa.Further work in this area, based on ammonites collected with the specime almost certainly provide refined chronology and geography of the Late Cretaceous dinosaur fa Africa.
During the Late Turonian, the coast of Iemb at 8 • S latitude) was at about 24
Fig. 2 -Summary of the geology of the Cretaceous of Kwanza Basin (Angola) based on Brownfield and Charpentier (2006) and Cow (1999).

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Fig. 6 -Phylogenetic relationships of Angolatitan adamastor and other sauropods.See text for explanation.